The Supreme Court of Canada has ruled in favour of three British Columbia medical workers who argued they developed breast cancer as a result of their jobs.

The cases involve Katrina Hammer, Patricia Schmidt and Anne MacFarlane, who worked in a lab at Mission Memorial Hospital.

The Workers' Compensation Board originally denied their applications for compensation benefits on the grounds their cancers were not occupational diseases.

But rulings by the Workers Compensation Administrative Tribunal in 2010 and 2011 overturned those decisions and linked the cancers to the workplace.

The British Columbia Court of Appeal, however, said the tribunal's decisions were unreasonable because there was no evidence that the women's cancer was caused by their work environment and the tribunal ignored expert advice to the contrary.

Enough evidence, court rules

But on Friday the Supreme Court ruled for the women, saying while the expert evidence might not have met a standard of scientific proof, it was enough to link their cancers and the workplace together.

"While the record on which that decision was based did not include confirmatory expert evidence, the Tribunal nonetheless relied upon other evidence which, viewed reasonably, was capable of supporting its finding of a causal link between the workers' breast cancers and workplace conditions."

But the court was not unanimous in its decision, with Justice Suzanne Côté filing a dissenting opinion.

"In my view, the original decision of the Workers' Compensation Appeal Tribunal is patently unreasonable. On my reading, there is no evidence — and certainly no positive evidence — capable of supporting a causal link between the workers' employment and the development of their respective disease," she wrote.